Molding machine monitoring system

ABSTRACT

A monitoring system for detecting molded material in molding machines with two platens, one of which has a plurality of die recesses and the other of which is removable from the first, has an array of photoelectric cells, each corresponding to a die recess, arranged to sense the condition of one of the recesses when the platens are separated and having different outputs corresponding to differences in conditions of the recesses, and has a switch arranged to prevent operation of the machine if the cells indicate the presence of molded material in any of the die recesses when the platens are separated. A television camera transmits an image of the recesses to a television receiver and the sensors are mounted on the screen of the receiver.

United States Patent Wilson Feb, 15,1972

[54] MOLDING MACHINE MONITORING SYSTEM [72] Inventor: Warren ThomasWilson, Saugus, Mass.

[73] Assignee: The Gillette Company, Boston, Mass.

[22] Filed: July 15, 1969 [21] Appl. No.: 841,885

[52] US. Cl. ..425/137, 18/2 HA, 18/16 C, 90/13.99, 425/145, 425/167,425/173 [51] Int. Cl. ..B29f l/00, B30b 15/28 [58] l ieldofSearch ..18/2HA, 16C, 17 W, 17 K, 18/30 CM, 30 CS; 90/1399 [56] References CitedUNITED STATES PATENTS 3,105,907 10/1963 Colten et al. ..90/13.993,222,724 12/1965 Soderquist ..18/17 W 3,303,537 2/1967 Mislan ...18/16OC X 3,341,888 9/1967 Bridge et ..18/2 HA 3,487,507 1/1970 Turk ..l8/17K3,525,382 8/1970 Devol Primary Examiner-J. Howard Flint, Jr.Attorney-Willis M. Ertman 57 ABSTRACT A monitoring system for detectingmolded material in molding machines with two platens, one of which has aplurality of die recesses and the other of which is removable from thefirst, has an array of photoelectric cells, each corresponding to a dierecess, arranged to sense the condition of one of the recesses when theplatens are separated and having different outputs corresponding todifferences in conditions of the recesses, and

has a switch arranged to prevent operation of the machine if I the cellsindicate the presence of molded material in any of the die recesses whenthe platens are separated. A television camera transmits an image of therecesses to a television receiver and the sensors are mounted on thescreen of the receiver.

4 Claims, 4 Drawing Figures MOLDING MACHINE MONITORING SYSTEM Thisinvention relates to a scanning system for injection molding machinesand, more particularly, to a system for controlling the operation of amolding machine in response to the condition of the mold. 7

ln molding machines of the type to which the invention relates the diemold includes a cavity portion disposed on a stationary platen and acooperating cover portion mounted on a movable platen. In the moldingprocess, after the movable platen is placed in sealing engagementagainst the stationary platen, molten thermoplastic material is injectedinto the cavity of the mold and allowed to cool and harden. The movableplaten is then moved away from the stationary platen and carries with itthe hardened molded material which is removed therefrom for subsequentsteps in the manufacturing process by suitable means, such as ejectionrods, mounted within the movable platen, which automatically propel themolded material from the movable platen when it has moved apredetermined distance from the stationary platen.

Occasionally a portion of the thermoplastic material injected into thecavity remains therein after the movable platen has been moved away fromthe stationary platen. If a second molding operation is performed whilethis previously hardened material remains in the cavity, the pressureresulting from the second injection of thermoplastic material will causethe mold to burst. Consequently, the condition of the cavity must beobserved and if plastic remains therein it must be removed-betweensuccessive operations of the molding machine. Conventionally, a humanattendant is required beside each machine to observe the condition ofthe cavity, to remove molded material, if necessary, and then to restartthe machine cycle.

Accordingly, it is an object of the present invention to provide asystem which automatically, efficiently, and reliably monitors thecondition of the die cavity between successive molding operationswithout requiring a human attendant beside each machine.

Another object of the invention is to provide for such a system withapparatus that is simple and inexpensive, automatically permitssuccessive operations when the cavity remains free from plastic residue,and automatically stops operation when plastic is left behindin thecavity.

A further object of the invention is to provide such a system whichobserves a number of cavities in a single molding machine die in greaterdetail and more rapidly than is possible with the human eye or existingdevices and may be employed to record the location of those cavities inwhich plastic remains most frequently- A still further object of theinvention is to provide a scanning system which permits observation of alarge number of cavities in many molding machines, while requiring onlyone attendant to supervise the machines and remove plastic which remainson a die surface after molding and then to restart the molding machine.

According to the invention a monitoring system for detecting moldedmaterial in molding machines with two platens, relatively movablebetween a first position in which a die cavity for receiving material tobe molded is formed and a second position in which the platens shouldcarry no molded material, one of the platens having a'plurality of dierecesses each with a first condition in which the cavity is free frommolded material and a second condition in which the recesses have moldedmaterial disposed therein, has an array of sensors, each correspondingto a die recess, arranged to sense the condition of one of the recesseswhen the platens are in the second position and having first and secondoutputs corresponding, respectively, to the first and second conditions,and has means responsive to the second outputs to signal the presence ofthe molded material in any of the recesses.

In a preferred embodiment the system also has structure arranged toprevent operation of the machine after the means signals the presence ofmolded material in any of the die recesses when the platens are in thesecond position and has means for releasing the structure to permit themachine to operate after the molded material has been removed from allof the recesses. The system includes a television camera arranged totransmit signals representative of the respective condition of each ofthe die recesses and a television monitor arranged to receive thesignals and to convert the signals to an image of the recesses on thescreen of the monitor. Each of the sensors is a cadmium sulfidephotocell mounted adjacent to the image of the corresponding recess onthe screen, arranged to discriminate between a first image of the recesswhen it is free of molded material and a second image of the recess whenit has molded material disposed therein, and having first and I secondoutputs respectively corresponding to the first and second images foreach recess. The means responsive to the second outputs is an electricalcircuit with first, second, and third switches, first, second, and thirdindicating lamps, and an alarm. The structure arranged to preventoperation of the machine is the first switch when it is open, themeansfor releasing the structure is the circuit, the circuit is arrangedto open the switch when at least one of the photocells has a secondoutput to close the switch when all of the photocells have a firstoutput. The circuit is arranged to energize the alarm when at least oneof the photocells has a second output and the second switch is arrangedto deenergize the alarm and to return the first switch to the closedposition when all of the photocells have their first output. The systemincludes at least one additional photocell arranged to energize thecircuit to open the first switch when the screen of the televisionmonitor is deenergized. The circuit has a photorelay arranged to beenergized and to energize the alarm and open the first switch when oneof the photocells has its second output and the third switch is arrangedto deenergize the photorelay when the third switch is in the openposition and to energize the photorelay when the third switch is in theclosed position and at least one of the photocells has its secondoutput. The third switch is arranged to be in the open position when theplatens are in their first position and to be in the closed positionwhen the platens are in their second position. The first indicating lampis arranged to be energized when the additional photocell has a secondoutput, the second indicating lamp is arranged to be energized when atleast one of the other photocells has a second output, and the thirdindicating lamp is arranged to be energized when the alarm is energized.

The system permits efficient supervision of a number of machines by oneattendant with greater reliability than human observation of anindividual platen, reduces the time lag required between successiveoperations, and provides sufficient discrimination to monitor thecondition of a large number of individual recesses.

Other objects, features, and advantages will become apparent from thefollowing description of a preferred embodiment of the invention, takentogether with the attached drawings thereof, in which:

FIG. 1 is a front elevational view of a scanning device, ac cording tothe invention, and an injection molding machine, the die cavity of whichis observed;

FIG. 2 is a front elevation, partly broken away, showing the televisionreceiver and photocells of FIG. -1 in greater detail;

FIG. 3 is a front elevation of the stationary platen of FIG. 1; and

FIG. 4 is a schematic wiring diagram of the circuitry of the scanningdevice of FIG. 1.

There is shown in FIG. 1 an injection molding machine 10 having amovable metal platen 12 arranged to be moved into mating engagementagainst stationary metal platen 14 and is arranged to receive moltenthermoplastic material through conduit 16. Platens l2 and 14 arearranged to define 16 die cavities, generally designated 18, when theyare in engagement and to cool the thermoplastic material in the mannerthat it hardens in the shape of the mold. Movable platen 12 is furtherarranged to be withdrawn and carry the molded plastic from platen 14after the plastic hardens and is provided with rods (not shown) forautomatically ejecting the molded plastic from the face of platen 14into trough 20, which communicates to a device, such as a conveyor belt,which carries the molded plastic structures to other machinery used inthe manufacturing process.

Television camera 22 is arranged to observe the recesses 24 in platen 14after platen 12 has been withdrawn therefrom by a predetermined distance(to be discussed more fully below) and to transmit the image totelevision receiver 26 upon the screen 28 of which are mounted l7cadmium sulfide photocells 30, 16 of which arranged to detect the imageof plastic material, if any, remaining in recesses 24 after platen 12has been withdrawn and to change an electrical characteristic inresponse thereto in the manner that an alarm will sound and the moldingmachine will discontinue operation until the plastic is removed and themachine is reset.

Referring to FIG. 3, platen 14 has 16 separate recesses 24 into whichmolten thermoplastic material is injected through conduit 16 and runners34, each runner feeding four recesses.

24. One each of 16 photocells, 30-1 to 30-16, observes the image of thecorresponding recesses 24, while the seventeenth photocell, 30-17,observes the raster of screen 28.

The detailed electrical circuitry corresponding to the apparatus ofFIGS. 1-3 is shown in FIG. 4 and is connected for operation with acommon I -volt AC source. Camera 22 and receiver 26 are continuouslyenergized and limit switch 36, which closes when platen 12 moves apredetermined distance from platen 14, is arranged to energize timedelay relay 38, which after a 5-sec0nd delay, closes normally opencontact 38-1 to energize the control relay 40. Photo relay 42 isconnected in series with photocell -17 and normally open contact 40-1 ofrelay 40, becomes energized after relay 40 has been energized whenphotocell 30-17 detects the raster on screen 28 and opens normallyclosed contact 42-1. Indicating light 44 is connected in series withcontact 42-1 and normally open contact 40-2 of relay 40 and is energizedif the receiver is turned off or there is no image on the screen forsome other reason. Control relay 46 is energized if relay 42 remainsdeenergized and contact 40-2 is closed, and closes normally open contact46-1, to energize alarm light 48, alarm bell 50, and control relay 52,and normally open holding contact 46-2. Relay 52 has normally closedcontact 52-1 connected in the control circuit 53 of the molding machinein the manner to shut down the machine when contact 52-1 is open and hasnormally closed contact 52-2 connected in series with relay 38.Photorelay 54 is connected in series with contact 40-1 and is energizedwhen one or more of photocells 30-1 through 30-16 detect plastic in oneor more of recesses 24 and closes normally open contact 54-1 to energizecontrol relay 56 and indicating light 58. Relay 56 has normally openholding contacts 56-1 and contacts 56-2 arranged to energize alarm light48, alarm bell 50 and relay 52 upon energization of relay 54. Resetbutton 60 is provided to deenergize all relays, indicating lights andthe alarm and to return the circuit to its initial position after thecondition which caused the machine to be shut down has been corrected byan attendant.

In operation, platen 12 is moved into engagement against platen 14 andmolten thermoplastic is injected through conduit l6 and runners 34 intorecesses 24. When the plastic has cooled and hardened, platen 12 ismoved away from platen 14 and carries the molded plastic pieceswith it.The pieces are when contact 38-1 closes, energizing relay 40 to closecontact 40-2, contact 52-1 in control circuit 53 remains closed and themolding machine automatically begins its next molding operation.

If, however, photocell 30-17 detects the absenceof a raster, photorelay42 remains deenergized, and contact 42-1 remains closed. When contact40-2 closes after the time delay, indicating lamp 44 and relay 46 becomeenergized and contacts 46-1, 2 close. Contact 46-2 holds relay 46 andlamp 44 in an energized state, while lamp 48, bell 50 and relay 52 areenergized through contact 46-1. Contact 52-] opens and the machine isshut down. The molding machine remains inoperative until an attendant,after observing alarm light 48 or hearing bell 50 and observing thatlamp 44 is energized, turns on receiver 26 and presses reset button 60after an image appears on screen 28.

When a piece of plastic has beenileft in one or more of recesses 24, oneor more of photocells 30-1 to 30-16 detects the plastic material andenergizes photorelay 54. Contact 54-1 closes, piece in mold indicatinglamp 58 and relay 56 are energized, and contacts 56-1 and 56-2 close tolock in lamp 58 and relay 56 and energize alarm lamp 48, bell 50, andrelay 52. Contact 52-1 opens and the machine shuts down. An attendantalerted by the alarm observes that piece in mold lamp 58 is energized,scrapes the plastic from those recesses 24 in which it has remained, anddepresses button 60 to release the circuit and resume operation.

The use of several scanning devices as disclosed above permits thesimultaneous operation of a number of molding machines, while requiringthe presence of a single attendant, who need only observe lights andbells rather than the complex contour of platen 14. Each device mayemploy additional photocells to monitorthe condition of runners 34, aswell as that of recesses 24, after each molding operation. In addition arecording device may be used in conjunction with the scanning device andcoupled to the individual photocells in 7 order to record the frequencyof pieces of plastic remaining in individual recesses after completionof molding operations in order that the recesses where sticking occursmost frequently may be detected and appropriate remedial action taken.

While a particular embodiment of the invention has been shown anddescribed, various modifications thereof will be apdeposited in trough20 by suitable means such as rods I mounted within platen 12. Whenplaten 12 moves a predetermined distance, it closes limit switch 36 andrelay 40 is energized after the desired time delay. If there is a rasteron screen 28, photocell 30-17 is energized and if no plastic remains inrecesses 24 none of photocells 30-1 to 30-16 is energized. Photorelay 42is energized and contact 42-1 opens, thereby opening the circuit toindicating lamp 44 and relay 46. Photorelay 54 remains deenergized andcontact 54-1 remains open so that indicating light 58 and relay 56remain deenergized.

Furthermore, contacts 46-1 and 56-2 remain open and lamp 48, bell 50 andrelay 52 are deenergized. Therefore,

parent to those skilled in the art and therefore it is not intended thatthe invention be limited to the disclosed embodiment or to detailsthereof, and departures may be made therefrom within the spirit andscope of the invention as defined in the claims.

What is claimed is: g

1. A monitoring system for detecting molded material in a moldingmachine having two platens, relatively movable between a first positionfor receiving molding material in die cavities formed between saidplatens and a second spacedapart position in which said platens shouldcarry no molded material, one of said platens'including a plurality ofdie recesses, each recess having a first condition in which the recessis free from molded material and a second condition in which said recesshas molded material disposed therein, said system comprising atelevision camera for sensing said one platen and provid ing a videosignal output representative of all of said plurality of die recesses ofsaid one platen, display means at a position spaced from said moldingmachine including a screen and means responsive to said video signal forproviding a visual display representative of said die recesses on saidscreen,

an array of photocells, each corresponding to a die recess and beingdisposed in fixed relation relative to said screen to sense thecondition of the image of the corresponding recess when said platens arein said second position, and having first and second outputscorresponding, respectively, to said first and second conditions, and

an electrical circuit having first switch means, said first switch meanshaving a closed position permitting said machine to operate and an openposition in which said machine does not operate, said circuit beingarranged to 'open said first switch means when one of said photocellshas a second output indicating the presence of molded material in amonitored die recess and second switch means arranged to return saidfirst switch means to said closed position when all of said photocellshave their first outputs.

2. The system according to claim 1 wherein said screen has an energizedcondition and a deenergized condition and said system further comprisesa sensor arranged to sense the condition of said screen and having firstand second outputs, respectively, corresponding to said energized anddeenergized condi-

1. A monitoring system for detecting molded material in a moldingmachine having two platens, relatively movable between a first positionfor receiving molding material in die cavities formed between saidplatens and a second spaced-apart position in which said platens shouldcarry no molded material, one of said platens including a plurality ofdie recesses, each recess having a first condition in which the recessis free from molded material and a second condition in which said recesshas molded material disposed therein, said system comprising atelevision camera for sensing said one platen and providing a videosignal output representative of all of said plurality of die recesses ofsaid one platen, display means at a position spaced from said moldingmachine including a screen and means responsive to said video signal forproviding a visual display representative of said die recesses on saidscreen, an array of photocells, each corresponding to a die recess andbeing disposed in fixed relation relative to said screen to sense thecondition of the image of the corresponding recess when said platens arein said second position, and having first and second outputscorresponding, respectively, to said first and second conditions, and anelectrical circuit having first switch means, said first switch meanshaving a closed position permitting said machine to operate and an openposition in which said machine does not operate, said circuit beingarranged to open said first switch means when one of said photocells hasa second output indicating the presence of molded material in amonitored die recess and second switch means arranged to return saidfirst switch means to said closed position when all of said photocellshave their first outputs.
 2. The system according to claim 1 whereinsaid screen has an energized condition and a deenergized condition andsaid system further comprises a sensor arranged to sense the conditionof said screen and having first and second outputs, respectively,corresponding to said energized and deenergized conditions of saidscreen, said circuit being responsive to said second output of saidsensor to open said first switch means and prevent operation of saidmachine when said sensor has its second output.
 3. The system accordingto claim 2 wherein said circuit further comprises a first indicatinglamp arranged to be energized when said sensor has said second output,and a second indicating lamp arranged to be energized when at least oneof said photocells has a second output.
 4. A system according to claim 1wherein said photocells are cadmium sulfide photocells.